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Old 07-27-2013, 11:20 AM   #1
vms150
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Member#: 172917
Join Date: Feb 2008
Chapter/Region: NESIC
Location: Southeastern, Massachusetts
Vehicle:
2004 WRX
WRB

Default Car Falters Violently Under Boost

Yesterday I was driving my car and as soon as I got into boost (between 5-10lbs) the engine pretty much fell on its face as if it hit the fuel cut off. It was violent. The car would stutter hard and the boost needle would shake violently. I would let off the accelerator and I could drive fine out of boost. This happened about a month ago but a bit differently. I would start the car and it would idle horribly for about 5 seconds then die. It was non-responsive for the most part to the throttle to try to keep it alive. I have checked for boost leaks, loose grounds and vacuum leaks to no avail. I installed a new fuel filter at that point just incase. The odd thing is the next day it worked fine and has since, until yesterday. BOTH instances were in the rain, I don't know if this is coincidence or possible part of the problem. Any help would be much appreciated. ALSO, no CEL or codes on the scanner.
Mod List for Reference:
port and polished td04
header back catless exhaust
GS EBCS
Warboro 255lph fuel pump
STI tmic
SPT intake
Wicked Innovations tune
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Old 07-27-2013, 12:30 PM   #2
WTFWJD014
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I woukd try a compression test and a leak down just to know the numbers are at a safe level. Does it run rich or lean? If you have logs that would be helpful too
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Old 07-27-2013, 12:51 PM   #3
BlazeRex
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Join Date: Dec 2010
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Location: Massachusetts
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02 WRX 05 LGT
Slow Automatics

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I'm located near you and can help. I've seen a bit of cars with the same issue, and as they get older I see it more and more often.

9/10 its bad plugs, a coil pack on its way out, or cam sensor failing.

PM me if you would like me to try and help.
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Old 07-27-2013, 12:56 PM   #4
vms150
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Join Date: Feb 2008
Chapter/Region: NESIC
Location: Southeastern, Massachusetts
Vehicle:
2004 WRX
WRB

Default

Blaze, if the issue persists I will definitely contact you. Thanks so much for the offer. I believe I may have tracked down the issue. It seems that what it rains hard a puddle forms on top of the knock sensor. I blew it out with compressed air and let the engine heat up for about 15 mins to dry it out and now it's fine.
Also, is there any way or testing for a bad coil pack? I don't mind just swapping plugs or cam sensors but the coil packs are rather expensive to change on a guess.
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Old 07-27-2013, 03:25 PM   #5
WMCCook29
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Location: Boston
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Quote:
Originally Posted by vms150 View Post
Yesterday I was driving my car and as soon as I got into boost (between 5-10lbs) the engine pretty much fell on its face as if it hit the fuel cut off. It was violent. The car would stutter hard and the boost needle would shake violently. I would let off the accelerator and I could drive fine out of boost. This happened about a month ago but a bit differently. I would start the car and it would idle horribly for about 5 seconds then die. It was non-responsive for the most part to the throttle to try to keep it alive. I have checked for boost leaks, loose grounds and vacuum leaks to no avail. I installed a new fuel filter at that point just incase. The odd thing is the next day it worked fine and has since, until yesterday. BOTH instances were in the rain, I don't know if this is coincidence or possible part of the problem. Any help would be much appreciated. ALSO, no CEL or codes on the scanner.
Mod List for Reference:
port and polished td04
header back catless exhaust
GS EBCS
Warboro 255lph fuel pump
STI tmic
SPT intake
Wicked Innovations tune
A wet MAF exhibits these symptoms - happens with short rams from time to time.
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